Bug 2176 - DGA mode detection sets imageHeight and imageWidth to 0

[James Wright]

  Added clamping of 16 bit values when copying mode info in "Xserver/Xext/xf86dga2.c"
which fixes this bug. Could some take a look and commit to CVS if its all good?

https://bugs.freedesktop.org/show_bug.cgi?id=2176

Cheers,
James